Re: Default :group in lisp/emacs-lisp/easy-mmode.el.

[Richard Stallman]

The use of custom-current-group seems like a bad practice to me.
It is unreliable to make one defun depend on whatever was lying around
from a previous defun in this way.  It has the result that moving
code from one place in a file to another changes its meaning.

So I think it would be better to document that define-minor-mode
and easy-mmode-define-global-mode default the group based
solely on the mode name.